The h Bar

user228700

11:00

:-)

user228700

Say, @Blue: What's your roommate like?

Anonymous

@Kaumudi.H I don't have one. I stay in my house. (Lucky me ;))

user228700

Ah, yes, I'd forgotten! :-)

user228700

Are you OK that you are missing ze hostel experience?

Anonymous

@Kaumudi.H I wouldn't trade my air conditioned room and home-made food for staying in a hostel without ACs. Moreover, I don't have to do things like washing clothes, cleaning my room, etc. By the way, I do have to spend a considerable amount of time with my classmates anyway. I don't think I'm missing much (expect a jerk roommate maybe :P).

user228700

11:05

> except a jerk roommate maybe

user228700

Right you are!

user228700

Oh, BTW, it has been pouring cats and dogs since 4 AM, so they have declared tomorrow a holiday!!

Anonymous

Does your roommate still irritate you?

John Rennie

Not since K buried her under the floorboards :-)

Anonymous

@Kaumudi.H Wow. Even we have holiday tomorrow and the day after! (For Mahalaya)

Anonymous

11:07

Puja holidays begins next week though

user228700

@JohnRennie SHHHHH.

John Rennie

@Kaumudi.H :-)

Anonymous

Woah. What's the story? ("floorboards") :P

user228700

@Blue No, not very much, thank you :-) Sometimes, she likes to shout at me very loudly but she addressed that issue and told me that she cannot help but do just that under stress.

Anonymous

@Kaumudi.H Some improvement at least ;)

user228700

11:10

Actually, no, she still does those same things as before. It has simply become less irritating now :-P

Anonymous

:P

user228700

In other news, I went out in the pouring rain to get a late lunch/early dinner and got soaking wet.

user228700

On the upside, I went on my friend's scooter and had an exciting time racing around on it :-P

user228700

Yes, it is stupid to race on a scooter in the rain, I realise :-P I didn't particularly care is all.

Anonymous

Buy some paracetamol tablets by today, along with a nasal spray and cough syrup. :d

user228700

11:15

Very exciting times, you see! I went out. SO exciting :-P

user228700

@Blue Lol, no, I'll be OK :-) Had me helmet on!

user228700

@JohnRennie Ya know, any person who needs to use such a setup to walk certainly can't wave it in the air!

John Rennie

@Kaumudi.H in the UK there's a stereotype of a grumpy old man waving his walking stick in the air in a temper. I was trying to come up with a variant of that, but yes waving a zimmer frame in the air isn't that likely :-)

user228700

No, no, I get it :-) I was trying to be funny; it seems that I failed, yet again :-P

user228700

Every time you mention waving stuff in the air, I picture this guy:

user228700

11:22

Ah, who am I kidding? The picture is never going to load :-/

user228700

user228700

Praise the Lord! It loaded at last!

John Rennie

Ah, yes. Up! :-)

user228700

Ohh, you've watched it, have you?

John Rennie

No. But my niece has seen it and told me about it.

user228700

11:30

Ah, nice :-)

user228700

Gah, stupid rain. I'm tired of the pitter-patter.

John Rennie

It's been raining a lot here in the last week, though yesterday was dry and touch wood today looks likely to stay dry. Just as well since I shall be off in search of food ina bit.

user228700

Ah, well, I hope it doesn't start pouring just as you set out! :-)

John Rennie

This was Friday's meal:

Actually that was half of Friday's meal since I ate two of them :-)

user228700

Wait, what sauce is that on top?

John Rennie

11:37

Jerk BBQ sauce. Hang on, I'll find a link ...

user228700

No, no, it's OK :-)

user228700

But wow, that looks great! :-) Very filling it must've been, no?

John Rennie

This is the sauce

I felt pretty full after eating two of those pizzas, though not too full to eat the chocolates I was given for fixing my Mum's friend's laptop :-)

user228700

Nice :-)

John Rennie

I'm not feeling inspired today though. I'll just wander into town and see if anything catches my eye.

user228700

11:42

Where is this town where you shop around looking for things to catch your eye? :-P

user228700

Every time you say that, I picture an Englishman walking around with his cycle in an Arabian street market :-P Oddly specific, hmm.

John Rennie

There are several large supermarkets in Chester. If I'm not in a hurry (like today) I'll cycle to them all and look to see what special offers they have.

user228700

All of them?! Wow.

John Rennie

There are four within a mile and a half of the city centre, so it's easy to pop into those. There are a couple more a few miles farther away, but I'll probably give them a miss.

Anonymous

@Kaumudi.H Chester is a small town. So I think that's possible. :)

John Rennie

11:46

Partly I visit them all just for the exercise.

user228700

@JohnRennie Right, right.

user228700

And here I am, 18 years old, getting fatter by the day, racing around on a scooter :-/

John Rennie

You cycle as well ...

Or have you given up since your brush with death? :-)

user228700

@JohnRennie Haha, no, no :-)

GPhys

in something like $\gamma +p\to \Delta^+$, can this still occur if the photon and proton have more energy than the rest mass of the $\Delta^+$ in the center of mass reference frame? I was told this is the interaction that you can use to find the proton energy limit above which protons will interact with the cosmic microwave background, but this is only possible with one specific proton energy then.

Can the interaction still occur with more energy if the Delta baryon immediately decays?

Anonymous

11:57

@heather I was watching the 3Blue1Brown Linear Algebra videos. It does have some great animations. :)

user228700

I gots to take a quick nap. See you all later :-)

Anonymous

Cya!

Balarka Sen

too much to learn

too little time

soon we all die

also goddamned internet is broken

heather

@Blue =)

user228700

12:33

@BalarkaSen Yours too?

Jasper

12:49

@Kaumudi.H Well, if you want, you can go running. Helps to lose weight and also good for the mind.

0ßelö7

13:30

@Kaumudi.H Unless you really need to know the formal definition of differentiability in the miltivariable case, I would ignore it and take a class on Differential analysis in Banach spaces later. Once you learn some topology and better notation it will be a breeze

And I'm your life as whatever you're doing you'll never once need the formal definition anyway

*in your life

Jasper

13:48

@0ßelö7 Are you kidding? You are telling an engineering student to read differential calculus in Banach spaces? lol

3

Anonymous

@Jasper She is a CS student though. I'm not sure if that classifies as core engineering. :P

Anonymous

Some CS students do go ahead and study a lot of advanced math

Jasper

@Blue Oh sorry I got it wrong. She is a computer science student? Hmm.

Anonymous

@Jasper Yup

0ßelö7

@Jasper did you even read what I wrote

Clearly not

Jasper

13:53

@0ßelö7 Yeah, sort of, kind of, the idea is there, lol. No need to be soooo precise.

0ßelö7

I can't parse that response

@Blue not analysis

Anonymous

@0ßelö7 Well, if she goes into theoretical Computer Science, she will need it.

0ßelö7

Reference?

user228700

Haha, no, I will not go into theoretical Computer Science :-) I will, however, go into Cognitive Neuroscience and I am told that I will need to learn lots of topology in that.

0ßelö7

Reference?

user228700

13:59

@0ßelö7 Me?

0ßelö7

I don't know what "lots of topology" is supposed to mean

Anonymous

@0ßelö7 springer.com/us/book/9780857294456

0ßelö7

@Blue One book is not a damn reference and you know that

some CS people might need analysis, sure

Anonymous

@0ßelö7 cs.stackexchange.com/questions/tagged/mathematical-analysis

Anonymous

@0ßelö7 That's what I meant.

0ßelö7

14:00

those are calculus questions

Sanya

@Blue this is not really much analysis beyond very very very basic stuff

heather

8

Q: What areas of mathematics support the study of cognitive science?

Which areas of mathematics can be formally studied in a cognitive science major? Or: which areas of mathematics can support the study of brain. Some areas that seem relevant would be: mathematical logic, graph theory, linear algebra. Is any element of topology relevant? Please direct to links/sou...

mathematical-psychology

user228700

@0ßelö7 Heck if I do, really. I have been learning some basic Topology and found out that its applications in Neuroscience are vast.

0ßelö7

As an analyst, I'm disappointed that you're trivializing my field :P

Anonymous

@Sanya w.r.t mathematicians. I agree.

0ßelö7

14:02

@Kaumudi.H such as?

I am genuinely curious

Jasper

@Kaumudi.H Do you have a nice book for learning topology?

user228700

Here, let me direct you to a video:

0ßelö7

@Jasper I have already given her books

Jasper

@Kaumudi.H If you just want to study general topology, I recommend General Topology by Stephen Willard. It is a cheap Dover book you can buy for a few dollars, and I much prefer it to more standard texts.

user228700

Your Mind Is Eight-Dimensional - Your Brain as Math Part 3 | Infinite Series

►

user228700

14:03

@heather Thanks, man! :-)

heather

@Kaumudi.H np - note that the most upvoted answer says topology isn't much used =P

0ßelö7

...man?

I knew it

Anonymous

"Your mind is 8 dimensional".....sounds like pop sci

0ßelö7

@Blue yes, I cringed

user228700

@heather I did, I saw that :-) Oh, well, I don't claim to know everything!

heather

14:05

neither do i, i just googled "topology in cognitive neuroscience" =P

0ßelö7

simplices

so it's combinatorics, not topology :P

user228700

@Blue It really isn't.

Jasper

@0ßelö7 Well, it's combinatorial topology, lol.

0ßelö7

@Kaumudi.H Honestly, unless I'm missing something here, they call this topology because that's sexier than combinatorics.

2

user228700

@0ßelö7 Hehe, I see.

user228700

14:07

@heather :-) Haha.

Jasper

After all, what is topology, what is combinatorics, these terms are not well defined.

0ßelö7

As Jasper says, this is combinatorial topology.

Jasper

You cannot give a simple answer to the question what is mathematics? What is love?

user228700

Right.

0ßelö7

Haddaway - What Is Love [Official]

►

Jasper

14:09

LOL

user228700

In any case, I'm not looking to learn Topology now. For the time being, I am focusing on getting good grades in all the courses I have to take this semester.

0ßelö7

@Kaumudi.H Go to a random paper on this and search for "open set." If you don't see that...it's not topology.

user228700

x'D I see.

0ßelö7

Or "neighborhood."

user228700

@0ßelö7 I use it to be an equivalent term to "Dude" and "Guy". They aren't gender specific.

0ßelö7

14:10

@Kaumudi.H In English, "man" is definitely gender specific.

Anonymous

Imo...you should perhaps learn a bit of biology on the side. That's more related to CN.

Jasper

By the way, what is the female equivalent of dude?

0ßelö7

@Jasper I would get banned for saying

Anonymous

@Jasper dudette

0ßelö7

@Blue no

heather

14:11

uh...

Jasper

Someone told me it is gurl.

0ßelö7

@Jasper that works

heather

i've used dude for people of both genders; that's a pretty standard use.

user228700

@0ßelö7 I know several Americans who use the word "man" to casually refer to female friends as well.

0ßelö7

@heather correct

user228700

14:12

@heather Yes, exactly.

Jasper

@0ßelö7 Man in English can refer to humans in general.

0ßelö7

@Kaumudi.H Lesbians?

@Jasper you're thinking of German

Anonymous

Lol.

user228700

::Facepalm:: No, man. Heck, in one specific case, a person used the word "man" to refer to his wife.

heather

in fact, i generally dislike the term dudette. and also, i agree with Jasper/Kaumudi, I've used "man" for both genders and have heard others use it similarly.

Jasper

14:13

Similarly, gay can be used for both sexes as well.

Anonymous

@heather It's informal (and meant for humor).

heather

@Blue "man"?

user228700

It's, erm, I don't believe that it's meant for humor, really.

user228700

Informal, yes.

0ßelö7

These are all informal terms anyway

heather

14:14

^

0ßelö7

Just refer to people by their titles and be done

heather

The hbar: where no one actually talks about physics.

Instead, we break mathjax and discuss food, etymology, and video games.

user228700

@heather That is correct! :-P

Jasper

And although many people use sex and gender interchangeably, I prefer using the term sex because that has a physical connotation, while gender has a cultural/psychological connotation.

0ßelö7

@heather and math

heather

14:15

and way too much math for a physics chat

@0ßelö7 yup

user228700

Oh, we haven't broken MathJax in a while.

user228700

Well, you all.

Jasper

The same applies to race (physical) and ethnicity (cultural).

0ßelö7

to be fair I haven't talked about math in a while

heather

@Kaumudi.H heh, i remember when I participated in that last - some of the TeX and friends people came in to wince.

user228700

14:15

x'D

Jasper

The TeX SE people are real experts.

user228700

How are you, BTW? I hardly see you around.

Jasper

Many of them write or maintain the tex packages we use.

heather

@Kaumudi.H me or someone else?

user228700

@heather You :-)

heather

14:16

@Kaumudi.H oh =P quite well, thanks. i've been working on various projects, plus homework/extracurriculars.

0ßelö7

you never see analysis in pop-sci

it's the worst field :(

heather

quiz bowl, robotics...

user228700

@heather Cool! :-)

heather

it's great.

Jasper

@heather I did check out some of your stuff on github. =D

user228700

14:17

What sort of projects, may I ask?

heather

@Jasper ::winces:: i'm so sorry.

most of that stuff hasn't been updated and/or is incomplete (though I did update one thing yesterday)

@Kaumudi.H trying to work through a conceptual physics text i got ahold of a while back, set up an experiment involving spontaneous parametric down conversion

0ßelö7

@Jasper I've been asked to do regularity theory for the Poisson equation on a manifold with boundary in my PDE class

wonder if I can get through it in an hour

heather

research various random topics for quiz bowl

Jasper

@0ßelö7 I had a professor who always drinks apple juice in class. When I asked him whether he would do so in the Galois theory class, he said 'Why not? After all, apples grow in the fields!'

0ßelö7

if I skip all but the final proof, maybe ;'D

heather

14:19

@Jasper lol

so, actual physics problem, if anyone here would be interested in giving me a hand

0ßelö7

ugh

heather

i'm trying to figure out what sort of lens i'd need to take a beam of light from this laser:

0ßelö7

this better be mathematical quantum mechanics or GR

heather

digikey.com/products/…

Jasper

@0ßelö7 I think you are a brilliant dude. Don't forget me when you win the Fields medal!

0ßelö7

14:20

OOOOOOOOOOOOOOPTICS

heather

and narrow it down to a diameter of 3mm

@0ßelö7 nope optics

sorry.

0ßelö7

@heather see my second post

heather

oooooooooooooooooptics, excuse me.

0ßelö7

@Jasper thanks

we all have to do a presentation so it's not special

a guy requested I do something on the Laplacian on a manifold with boundary

so basic regularity theory makes sense

Anonymous

@heather What's the question?

heather

14:22

oh, btw, i just noticed an error in your profile @0ßelö7 - it should be interests

plural.

0ßelö7

@heather why are you stalking me

Jasper

@heather lol

0ßelö7

@heather was it always like that?

user228700

@heather I didn't even understand those words.

heather

i think? @0ßelö7

Spontaneous parametric down-conversion

Spontaneous parametric down-conversion (also known as SPDC, or parametric scattering) is an important process in quantum optics, used especially as a source of entangled photon pairs, and of single photons. == Basic process == A nonlinear crystal is used to split photon beams into pairs of photons that, in accordance with the law of conservation of energy and law of conservation of momentum, have combined energies and momenta equal to the energy and momentum of the original photon and crystal lattice, are phase-matched in the frequency domain, and have correlated polarizations. The state of the...

0ßelö7

14:23

@Jasper idk if I should try to do beamer

heather

basically: shoot a photon through two shiny crystals, every now and then out come two entangled photons.

Jasper

@heather Yes, it should definitely be interests there.

heather

@Blue I guess i'm asking how to figure out the lens dimensions as to narrow beam diameter to 3mm

Jasper

@0ßelö7 Beamer goes well with pgf and pgfplots for diagrams and plots respectively. All in the same family.

0ßelö7

@Jasper I very rarely need pictures

heather

14:25

i've looked at the lensmaker's equation as per my dad's suggestion, but i didn't see how that was relevant - i just got more confused, tbh

0ßelö7

Imo if you need pictures your proof is bad

Jasper

@0ßelö7 However, the beamer manual is over 200 pages long, but the tutorial should get you started, I think.

0ßelö7

oh, no

I mean do beamer for this presentation

I can use beamer

Jasper

Oh I see. It's up to you!

Anonymous

@heather You can use a convex lens coupled with a concave one to adjust the beam diameter. It should be basic ray optics.

heather

14:26

::eyes bug out::

wow

Jasper

I am old-fashioned so I prefer using chalk and blackboard.

heather

okay, i'll look that up @blue, thanks

Jasper

But these days even old professors use beamer as well.

0ßelö7

@Jasper that's not nearly as fast as beamer

and I have to get through a significant amount of analysis

Jasper

@0ßelö7 Yes, but I like to write and explain and think at the same time while presenting.

@0ßelö7 I guess if you do have a lot of equations to show, then beamer would be good.

0ßelö7

14:28

I should ask the prof if I can get two classes. I really need a while to set up Sobolev spaces

Jasper

Yeah, you can try asking for more time.

heather

$d_f = (4/\pi) M^2 \lambda F_L / d_{in}$

0ßelö7

wtf

heather

where

$d_f $= focus diameter, $M^2$ = beam quality, $\lambda$= laser wavelength,
$F_L$ = focal length of focusing lens, $d_{in}$ = diameter of incoming beam

0ßelö7

can you not use mathjax :P

heather

14:30

@blue is that right ^

@0ßelö7 heh =P

Balarka Sen

did i miss shit

Prathyush Poduval

a lot

Mithrandir24601

@heather for type I: :)

heather

@Mithrandir24601 yeah, that was an extreme oversimplification =)

Balarka Sen

@PrathyushPoduval i'm a scatman skrabadabadib da didabdib tell me all about it

i got the beat wrong

Prathyush Poduval

14:35

@BalarkaSen thats Wonderful :P

@BalarkaSen What beat?

heather

hmm...how can i figure out $M^2$...

reveal your secrets to me DigiKey

Prathyush Poduval

@BalarkaSen I found This part quite attractive

but still can't beat epic sax guy.....

Balarka Sen

the scatman is great, yep

you should check out KSI's epic sax guy prank video

here

Prathyush Poduval

@BalarkaSen Yah seen that :') :P

Balarka Sen

good, you're on track

Prathyush Poduval

14:44

the ass-shaking was quite awesome

user228700

@heather: Aw, man, did you break MathJax again? x'D

Balarka Sen

unfortunately KSI mostly makes disssshhh tracks nowadays

heather

@Kaumudi.H nope

Anonymous

Balarka Sen

which are shit

Anonymous

14:44

Laser beam quality

In laser science, laser beam quality defines aspects of the beam illumination pattern and the merits of a particular laser beam's propagation and transformation properties (space-bandwidth criterion). By observing and recording the beam pattern, for example, one can infer the spatial mode properties of the beam and whether or not the beam is being clipped by an obstruction; By focusing the laser beam with a lens and measuring the minimum spot size, the number of times diffraction limit or focusing quality can be computed. Anthony E. Siegman was the first to propose the formalism for a laser beam...

Prathyush Poduval

I didn't watch any other of KSI

Balarka Sen

dont

Anonymous

A beam profiler might be useful

user228700

@heather Ah, OK, it works now, after I reloaded the page :-)

Prathyush Poduval

How's life going on for you btw @BalarkaSen?

Anonymous

14:46

@heather Check the wiki article and the citations. I don't have much experience with lasers. Also, this: researchgate.net/post/…

heather

@Blue yes, i saw that, but the data sheet for the diode doesn't give any of those values =/

Balarka Sen

@PrathyushPoduval Not bad. Trying to strike up a balance between math, school and memes.

Prathyush Poduval

@BalarkaSen If you say so, it really must be quite bad :P

Balarka Sen

Working well so far...

0ßelö7

.-.

Anonymous

14:47

@heather Then you might have to measure them manually

heather

=/

user228700

@BalarkaSen Is your internet broken as well?

Balarka Sen

it's better right now it seems

user228700

Same.

Balarka Sen

excellent

Anonymous

14:48

@heather en.wikipedia.org/wiki/Laser_beam_profiler#Beam_quality

Prathyush Poduval

@BalarkaSen nice, when do yo're hoidays start?

@BalarkaSen use bsnl

Qmechanic

@BalarkaSen : When that song came out 20 years ago, I thought he looked like 't Hooft. :D

user228700

@BalarkaSen Do you think you'll attend your farewell?

heather

@Blue okay. thank you for your help!

i really appreciate it.

Balarka Sen

@Qmechanic hahah I don't actually know how t'Hooft looks like

't Hooft, misapostrophed.

@Kaumudi.H If my fare goes well, at least.

Anonymous

14:51

@heather Welcome. BTW I really need to learn about lasers. I don't know much. :P

Balarka Sen

@PrathyushPoduval Next week.

Prathyush Poduval

nice, midterms over yet?

Qmechanic

@heather: I think your comment here is perfect and to the point.

Balarka Sen

If by midterm you mean pre-test, yeah.

heather

@Qmechanic thank you.

Prathyush Poduval

14:54

@BalarkaSen don't know whats pretest. I was talking 'bout the test which is held i the middle of the year. Whats the duration of holidays there?

Balarka Sen

it's about uh 3/4th a month long

0ßelö7

@b

wtf

Prathyush Poduval

nice

0ßelö7

there is something wrong with stack exchange

Balarka Sen

@Blue It's not, though.

There's some actual nontrivial math going on there. The way the parsed it is pop-math sounding.

Anonymous

14:57

@BalarkaSen At least by watching the video it didn't seem like that. If true, I'd like to know the details.

Anonymous

I didn't watch the full video though

Balarka Sen

I don't think I have watched that video.

It's a complicated thing about the clique complex of the neural complex in our brain being experimentally found to have certain betti numbers that point to 11 dimensionality

Emilio Pisanty

@heather don't waste your time re-collimating

Anonymous

blog.frontiersin.org/2017/06/12/…

Anonymous

Interesting

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